The present invention relates to electrical connectors and, more particularly to hermetically sealed electrical connectors adapted to be mounted on the wall of a sealed chamber. Hermetically sealed electrical connectors, also known as "electrical feedthrus", are used to connect electrical components located within a hermetically sealed chamber to complementary electrical components--which may include a power source--located outside of the chamber, and are mounted on a wall of the chamber such that gases and/or radiation within the chamber cannot escape through the connection between the connector and the wall.
Hermetic connectors may consist of a jam nut housing having a hex-shaped head, adapted to be grasped by a wrench, and a threaded shank of reduced diameter extending from the head, so as to form an annular flange. The housing is attached to the wall of a pressure vessel or other sealed container by inserting the threaded shank through a hole in the wall of approximately the same diameter, then threading a jam nut over the threaded shank to clamp the annular flange against the portion of the wall immediately surrounding the hole. To provide a hermetic seal between the housing and wall, the annular flange is provided with an O-ring, made of a flexible material such as silicone, which is deformed to seal the opening when the jam nut clamps the flange against the wall.
The center of the jam nut housing may contain a pair of receptacles, and these often are of the pin and socket type. The pins and sockets of the receptacles are connected in pairs by wires which are embedded in a body of solid epoxy, glass or ceramic which is bonded to and forms a hermetic seal with the wires, jam nut housing and receptacles. The receptacles also include a threaded collar or bayonet mount which is shaped to receive a matingly threaded collar of a plug, and an insert, preferably made of diayll phthalate, which serves as a matrix to support the pins and sockets. Typically, both the threaded collar and the insert are bonded to the epoxy core of the housing.
In another type of connector, lengths of insulated wires are embedded in the epoxy body so that their ends protrude from the housing. The ends of the wires can be connected to electrical components on both sides of the wall on which the housing is mounted.
A disadvantage with hermetic connectors such as these is that, to replace the receptacles or wires of a connector, it is necessary to replace the entire connector, which requires the breaking of the hermetic seal formed between the connector and the wall to which it is attached. For example, in order to substitute connector of the previously described type having a seven-pin receptacle for one with a six-pin receptacle, it is necessary to remove the jam nut from the threaded shank, withdraw the six-pin housing from the hole in the chamber wall, then insert the seven-pin housing through the hole and seal it to the wall by tightening down the jam nut on its shank.
However, it is known to provide a controlled environment chamber with a permanent housing that supports a replaceable inner member. For example, in Woolsey U.S. Pat. No. 3,475,808, a replaceable glove is disclosed which is adapted to be mounted on an annular port permanently fixed to the wall of a controlled environment chamber. The cuffs of both the original and replacement gloves are slipped over mounting rings and held thereon by O-rings, the mounting rings including set screws which engage grooves formed on the port.
To change gloves, the new glove is placed inside the original glove so that the mounting rings of the gloves abut each other within the port, but only the O-rings of the original mounting ring abut and make a seal with the port. A guide ring is slipped over the replacement mounting ring so that it is interposed between that ring and the port, the latter having an offset sized to compensate for the added thickness of the guide ring. A push ring is inserted through the guide ring and contacts the replacement mounting ring, pushing that ring to the location formerly occupied by the original mounting ring, and pushing the original mounting ring out of the port. The replacement ring is then attached to the port by set screws, and the guide and push rings removed.
A disadvantage with this type of device is that additional equipment is required to effect a replacement of gloves, thereby increasing the overall cost of the device. Furthermore, the system is designed to utilize the relatively narrow mounting rings and provides access to the inner surfaces of these rings for such operations as tightening set screws. Such components would be entirely inappropriate for use with hermetic connectors which are elongate and have solid interiors.
Accordingly, there is a need for an electrical connector in which the receptacles can be replaced without breaking the hermetic seal formed between the connector and associated wall, thereby enabling the receptacles to be replaced without danger of the exterior of the sealed chamber becoming contaminated by the contents of the interior of the chamber. In addition, such a connector should be relatively economical to manufacture and should be sized to be mounted in the same areas and through the same openings as the aforementioned prior art connectors.